1. Field of the Invention
The invention relates to an ink cartridge which is detachably mounted on a head holder which is provided to an ink jet printer. In particular, it relates to an ink cartridge in which the ink volume can be increased while miniaturizing the head holder and the ink cartridge can be prevented from being erroneously mounted on the head holder.
2. Description of Related Art
There have been hitherto proposed various cartridges which are applicable to ink jet printers. Generally in a color printing ink jet printer, four ink cartridges which are independently filled with, for example, four colors of colored ink (black, magenta, yellow, cyan) are mounted on a head holder.
A conventional ink cartridge which is used for this type of ink jet printer will be described with reference to FIG. 13. FIG. 13 is a cross-sectional view showing an ink cartridge mounted on a head holder.
In FIG. 13, the head holder 100 has a pair of side walls 101, and a plurality of partition walls 103 (three partition walls are shown in FIG. 13) are formed on a bottom wall 102 which is formed between the side walls 101. An ink cartridge 104 filled with ink (not shown) is mounted between the respective partition walls 103. Each ink cartridge 104 comprises an ink tank 105 which is designed in a substantially rectangular parallelepiped shape having an opening at the upper portion thereof. A cartridge lid 106 is welded to the peripheral edge of the opening of the ink tank 105 to close the ink tank 105.
The peripheral edge of the ink tank 105 and the carriage lid 106 are generally welded to each other by an ultrasonic welding method and, particularly, the welding surfaces of the ink tank 105 and the cartridge lid 106 are welded to each other by a shear welding method which provides a strong welding force. When the shear welding is performed as described above, the outer side portion of each projection 107 formed on the lower surface of the cartridge lid 106 is welded to the inner side portion of a step portion at the peripheral edge of the opening which is formed in the ink tank 105. Therefore, in consideration of the requirements of shear welding, the thickness of the peripheral edge of the opening in the ink tank 105 must be set to 1.5 mm at a minimum. In view of the above requirement, as is apparent from FIG. 13, the ink tank 105 is designed so that the thickness of each side wall 108 of the pair of confronting side walls 108 is set to 1.5 mm over the whole body.
The conventional ink jet recording apparatus as described above is disclosed in Canadian Patent Application No. 2,100,977 (Japanese Laid-open Patent Publication No. Hei-6-40043).
In the ink cartridge 104 as described above, each side wall 108 of the ink tank 105 is designed to have an uniform thickness over the whole body thereof (1.5 mm). However, the thickness of each side wall 108 is excessively large for a disposable ink cartridge and, thus, it must be further thinned.
Further, with respect to each partition wall 103 formed on the bottom wall 102 of the head holder 100, it is required to keep the thickness of the partition wall 103 to the minimum thickness at which it can be formed, and also it is required to reduce the width of the head holder 100 as much as possible in order to miniaturize a carriage on which the head holder is mounted. Therefore, the width between the respective partition walls 103 is set to substantially a fixed value. Accordingly, when the thickness of each side wall 108 of the ink tank 105 is set to a large value as described above, the volume which can be secured in the ink tank 105 is reduced by the amount corresponding to the thickness, so that the amount of ink stocked in the ink cartridge 104 is reduced. In other words, in order to stock a constant amount of ink into the ink cartridge 104, the ink cartridge 104 must be designed to have a large size. This causes the head holder 100 to be large in size, and thus the carriage is also large in size.
Further, in the ink cartridge 104, an ink supply port 109 is formed at the lower position and an ink supply member, provided with an ink filter at the end face thereof, which serves to supply ink to an ink jet head (not shown in FIG. 13) and is provided to the head holder 100, is inserted into the ink supply port 109. The ink cartridge 104 has the same shape at the upper and lower portion thereof, so that there may be a case where the ink supply member which should be inserted into the ink supply port 109 will oppose a portion of the ink cartridge 104 other than the ink supply port 109, i.e., a wall of the ink tank 105, and the ink supply portion is damaged.